U.S. Pat. No. 1,949,360 discloses a process of preparing alumino-silicate particles by mixing aqueous solutions of sodium silicate and sodium aluminate, allowing the mixture of solutions to gel, freezing the gel at -10.degree. to -5.degree. C. without freezing or precipitating solutes contained therein, and thereafter thawing the gel and isolating, washing and drying the resultant particulate product. The art teaches, in general, that dissolved impurities or by-products, such as salts, either should be removed from the gel before it is frozen or they should not be allowed to precipitate during the gel-freezing step.